This invention relates to an air bag device which is provided, for instance, at the passenger's seat in an automobile.
A conventional air bag device of this type comprises an air bag which is folded up and accommodated therein; an inflator for supplying gas into the air bag; and a casing surrounding and supporting the air bag and the inflator.
To facilitate combining the air bag and the inflator with the casing, the casing is made up of two parts, namely, an upper case and a lower case.
The conventional air bag device whose casing is made up of the upper and lower cases suffers from the following difficulties. Upon inflation of the air bag, the casing is greatly shocked, so that the upper and lower cases may be deformed at the coupling parts thereof. Thus, the sealing of the casing may be impaired. The casing is most greatly shocked near the gas jetting outlets of the inflator adapted to supply gas to the air bag, and therefore, the above-described difficulty is most likely to occur near the gas jetting outlets of the inflator.
Hence, in the conventional air bag device having a casing comprised of the upper and lower cases, the wall thickness of those cases is increased, or reinforcing ribs or flanges are employed, to increase the mechanical strength of the portion of the casing which is located near the gas jetting outlets of the inflator.
However, increasing the wall thickness of the cases, or providing the reinforcing ribs or flanges results in an increase in weight of the casing.